1. Field of the Invention
Aspects of the invention relate to a door opening and closing unit, and an image forming apparatus having the same, and more particularly to a door opening and closing unit capable of controlling a rotating speed of a door while the door rotates, and an image forming apparatus having the same.
2. Description of the Related Art
In general, an image forming apparatus forms an image on a printing medium according to a printing signal supplied from a host apparatus. An image forming apparatus may include a printing medium feeding unit that stores and feeds a printing medium, an image forming unit that forms an image on the printing medium fed by the printing medium feeding unit, and a discharging unit that discharges the printing medium with the image formed thereon outside the image forming apparatus. An image forming apparatus may be a monochrome image forming apparatus in which a monochrome image is formed on a printing medium using a single color, such as a black-and-white image formed using a black color, or a color image forming apparatus in which a color image is formed on a printing medium using a combination of colors, such as a color image formed using yellow, magenta, cyan, and black colors.
FIG. 1 is a diagram of a color image forming apparatus 10 according to the related art. The image forming apparatus 10 includes a door 20, a printing medium feeding unit (not shown) that stores and feeds a printing medium P in the direction indicated by the straight single-headed arrow, developing devices 30 provided for each of four colors yellow (Y), magenta (M), cyan (C), and black (K) that store a developer and supply the developer in the form of an image to be transferred onto the printing medium, a printing medium conveying belt 23c that conveys the printing medium to each of the developing devices 30, a belt driving unit 23a, 23b that drives the printing medium conveying belt 23c, and transfer units 25 respectively provided for each of the developing devices 30 that transfer the developer supplied by the developing devices 30 onto the printing medium. Each of the developing devices 30 includes a photosensitive body 31 on which an electrostatic latent image is formed and then developed by a developer. The printing medium conveying belt 23c, the belt driving unit 23a, 23b, and the transfer units 25 are mounted on the door 20. The door 20 is rotatably mounted so that the door 20 can be rotated between a closed position as shown in FIG. 1, and a fully open position (not shown) as indicated by the curved double-headed arrow.
During an image forming operation of the image forming apparatus 10, a printing medium fed by the printing medium feeding unit (not shown) is conveyed by the printing medium conveying belt 23c to contact the photosensitive bodies 31 of the developing devices 30. The transfer units 25 apply a predetermined transfer voltage to a rear surface of the printing medium conveying belt 23c to transfer the developer in the form of an image from the photosensitive bodies 31 onto the printing medium to form an image on the printing medium.
If the printing medium jams between the developing devices 30 and the printing medium conveying belt 23c, the door 20 is opened to separate the printing medium conveying belt 23c from the developing devices 30 to enable easy removal of the jammed printing medium. Also, if the developer stored in the developing devices 30 is used up, the door 20 is opened to separate the printing medium conveying belt 23c from the developing devices 30 to enable the developing devices 30 to be replaced.
However, if the user lets go of the door 20 after opening it and before the door 20 has reached the fully open position, the door 20 will rotate at a high speed until it comes to a sudden stop in the fully open position, which will cause an impact to be applied to the door 20. The impact may be quite large because the door 20 is heavy since the printing medium conveying belt 23c, the belt driving unit 23a, 23b and the transfer units 25 are mounted on the door 20.
The impact applied to the door 20 causes an impact to be applied to the printing medium conveying belt 23c and the transfer units 25, thereby deforming the printing medium conveying belt 23c and the transfer units 25. If the printing medium conveying belt 23c is deformed, a color registration error occurs, thereby deteriorating a printing quality. Also, if the transfer units 25 are deformed, the time when the developer is transferred from the developing devices 30 to the printing medium and the value of the transfer voltage are mismatched among the transfer units, thereby deteriorating the printing quality.